Mammalian steroid 5.alpha.-reductase, an enzyme present in mammalian tissues including skin, male genitalia and prostate gland, catalyzes the conversion of the steroidal hormone testosterone to the steroidal hormone dihydrotestosterone (17.beta.-hydroxy-5.alpha.-androstan-3-one). Testosterone and dihydrotestosterone (DHT) are both androgenic hormones and they are the primary androgenic steroids in males. These steroids are responsible for the physical characteristics which differentiate males from females. DHT, however, is much more potent than testosterone as an androgen and it acts as an end-organ effector in certain tissues, particularly in mediating growth. Furthermore, the formation of DHT occurs primarily in the target cells themselves as a result of the reduction of testosterone by 5.alpha.-reductase.
It is known that skin responds to androgens and is an active site of androgen metabolism. In particular, testosterone is converted to DHT in the skin by the action of 5.alpha.-reductase. Testosterone metabolism in the skin may at times be abnormally excessive and have undesirable effects as a result of the DHT formed. Thus, there is considerable evidence that DHT is involved in the pathogenesis of acne, including acne vulgaris, as well as other androgen associated conditions [See Price, Arch. Dermatol. 111, 1496 (1975)]. Agents which are capable of blocking the formation of DHT from testosterone in skin, such as by inhibiting the activity of 5.alpha.-reductase, would therefore be useful in the treatment of acne.
In addition, other physical conditions and disease states, including benign prostatic hypertrophy, androgenic alopecia (common baldness caused by androgen in genetically susceptible men and women), seborrhea and female hirsutism, are also associated with elevated androgen activity and could be treated by the administration of 5.alpha.-reductase inhibitors. [See T. Liang et al., Endocrinology 117, 571 (1985); J. R. Brooks et al., Steroids 47, 1 (1986); J. R. Carlin et al., Journal of Chromatography, 427, 79 (1988).] Thus, agents which are capable of blocking the formation of DHT from testosterone by inhibiting the effects of 5.alpha.-reductase would also be effective in the treatment of these conditions.